How to calculate BTU output?

tea and coffee · 24-07-2013 12:46am #1

I have worked out how to convert 50 delta to 60 delta so I can get the radiators on a level playing field. but now how to calculate the BTU... I ahve looked at 3 different online caluculators and they all come up with a different measurement for the same room

e.g. 4 x 4 x 2.5 m3 room. One calcultors says 3338, another 4500, another 5200. Approx)

What is the most accurate way?

Thanks

shane0007 · 24-07-2013 7:37am

The 50 delta & 60 delta refers to the delta T & the 50 or 60 refers to the return temperature depending on the delta T.
50 delta is referring to condensing boilers which require a delta T of 20 so if 70 being the flow temperature, you would end up with a return of 50. You will notice rad size being larger on the 50 than the 60 to give the 20 DT. On the 60 delta it is working of circa 10C DT so return of 60 from a flow temperature of 70. This would be for standard efficiency boilers.

LIFFY FISHING · 24-07-2013 9:25am

For years the rule was ; lenght x breath x height x 6 = your btu requirements & its as accurate as will ever be required and then crossreferance your figures against the rad charts.

tea and coffee · 24-07-2013 9:26am

Thanks Shane. Yes the European rads are in 50 delta and the sizes I need are bigger anyway as they arent as efficient a radiator.
My issue now is trying to work out which actual radiator i need for which room. Every online calculator is giving me a different figure of btu needed to heat my room so I dont know which one to trust.
They are all wildly different numbers.

tea and coffee · 24-07-2013 9:28am

Thanks LF. Some calculators were asking about dbl glazing, north facing walls, french doors and how warm do I like my house?!?!?!?!
I will see what figures i get now using your method. Cheers

Outkast_IRE · 24-07-2013 10:07am

tea and coffee wrote: »

Thanks LF. Some calculators were asking about dbl glazing, north facing walls, french doors and how warm do I like my house?!?!?!?!
I will see what figures i get now using your method. Cheers

That's because a radiator is sized to cover the heat losses from that room, the amount of glazing, insulation etc etc makes a massive difference in the size of rad needed.

How to calculate BTU output?

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